This invention relates to a strap reserving control device for a strapping machine, particular to one able to quickly adjust and stably control the length or amount of the packaging strap stored in a strap reserving room
A conventional strapping machine has a strap reserving control device for controlling a preset length of a packaging strap stored in a strap reserving room to let the packaging strap guided out for strapping an object such as a carton.
The conventional strap reserving control device 10, as shown in FIGS. 1 and 2, has a balancing rod 11 and a press rod 12 respectively secured at the opposite ends of a rotating shaft 13. The rotating shaft 13 is pivotally inserted in a shaft sleeve 14 at the outer side of a separating plate 21 of a strap reserving room 20, letting the balancing rod 11 and the press rod 12 respectively positioned at the inner side and the outer side of the separating plate 21. Then, the shaft sleeve 14 is secured around with a fixed base 15 having one side extending outward and making up a support frame 151, which is provided with a micro-switch 16 on one side, and a twisting spring 17 and a stop rod 18 on the front side 152. The twisting spring 17 has its lower end extending downward and forming a hook 171 for holding the bottom edge of the support frame 151, and its upper end provided with a press-stopping member 172 extending horizontally above the stop rod 18, with the bottom edge of the and of the press rod 12 pressing on the press-stopping member 172 to avoid the press rod 12 pressing directly on the press button 161 of the micro-switch 16.
In operating, as shown in FIGS. 3, 4 and 5, firstly, start a strap feed device 40 to guide the packaging strap 30 to move into the strap reserving room 20 along the top edges of the balanced rods 11, with the packaging strap arranged to overlie on the left side and the right side on the balancing rods 11. At this time, in case the total weight of the packaging strap 30 in the strap reserving room 20 and the overlying tension therebetween is larger than the resilience of the press-stopping member 171, the balancing rods 11 will be pressed downward and the rotating shaft 13, by interaction, will synchronously actuate the press rod 12 to incline downward. Simultaneously, the bottom edge of the end of the press rod 12 will press on the press-stopping member 172 as well as on the press button 161 of the micro-switch 16, which immediately sends out a signal to turn off the power of the strap feed device 40 to stop guiding the packaging strap into the strap reserving room 20, thus finishing one round of strap reserving.
On the contrary, when the packaging strap 30 in the strap reserving room 20 is guided out for strapping an article to be strapped, the force on the balancing rods 11 vanishes, and the press-stopping member 172 recovers its resilience, pushing the press rod 12 to incline upward to separate from the press button 161 of the micro-switch 16, which in the mean time sends out a signal to turn on the power of the strap feed device 40, which is then started to guide the packaging strap 30 again into the strap reserving room 20 for strapping in a next round.
However, in a conventional strap reserving control device 10, the twisting spring 17 controls the strap-reserving amount in the strap reserving room 20 by its resilience. Under this condition, if a strapping machine is in use, the press-stopping member 172 of the twisting spring 17 will be pressed repeatedly by the press rod 12, and hence the twisting spring 17 is liable to become tired in its elasticity and loose, weakened and even damaged, not only shortening the service life of the machine, but also failing to stably control the length or amount of the packaging strap guided in the strap reserving room 20, and even resulting in insufficient supply of a packaging strap in the strap reserving room 20. Besides, the resilience of the twisting spring 17 is constant and impossible to be adjusted so the strap reserving amount set in the strap reserving room 20, which is controlled by the twisting spring 17, can not be adjusted by the strap reserving control device 10.
The objective of the invention is to offer a strap reserving control device for a strapping machine, applying a lever structure formed between a balancing weight device and a balancing rod to stably control the length or amount of the packaging strap stored in a strap reserving room, able to prolong the service life of the machine and lower cost for maintenance and repair.